Manufacture of hydroazo derivatives.



,. UN TED STATES .PATE NT o roE.

OTTO DIEFFENBAUIL OF DARMSTAD T, GERMAXY.

mANuFAcruns OF HYnRoAzo DERIVATIVES.

no. 833,513i

Specification ofLetters Patent.

Application filed March 28, 1906. Serial No. 308.616-

To all it may concern.-

-Be' it known that I, OTTO DIEFFENBACH,

, rofessor,"a subject of the Grand Duke of esse, and a-resiclent of Darmstadt', Grand Duchy of Hesse-Darmstadt, Germany, have invented new and useful Improvements in the Manufacture of Hydrazo Derivatives, of

. .plete Specification.

which the following is a full, clear, and com- The manufacture of hydrazo bodies, -as

'hydrazobenzene and its homologues, by electrolytic reduction ofthe corresponding nitro,

"azoxy, or azobodies suspended 1n the solution that during the process the reduction prodnets are precipitated in a solid form and are apt to stick to the cathodes and diaphragms,

so that they can only with difficulty be removed from the apparatus and .at the expense oil the durability of the latter, Besides, this coating or partial insulating of the cathode often causes a considerable rise of electric tension,- and consequently a useless 3. formed smoothly and with avoidance of the consumption of current. 1 I I have now found that the manufactureof hydrazo bodies by electrolysis can be perspecified defects if convenient solvents for the reduction roducts, which, however, should not be itse f soluble in water as, for instance benzene, toluene, xylene, &c. are added to the electrolytes. Inasmuch assuch solvents take up the reduction products, they prevent the objectionable precipitations on the oathodes and diaphra ms, and since at the end of the electrolysis t ey fioaton the electrolyte they can easily be removed from'the cathode com artment, together. with the reduction r0 ucts, without removin the electrolyte tself and without submitting the cathodes and diaphragms to a lon cleaning noxious to their durabilit A furt er advantage of additions of this 'nd is that they render, it possible to remove in a simple manner the azoxy derivatives which are present, besides the hydrazo derivatives,from the latter andto return them to'the electrolyte by adding directly to the benzene, toluene, or xylene solution the hydrochloric acid necessary to transform the hydrazo derivatives into the correspondmg gether with a fresh benzidine compounds. We thereby attain an aqueous solution of benzidine hydrochlorid (or of the hydrochlorid of another paradiamin of the benzidine series) which can easily be-separated from the upper layer of benzene which contains the azoxy body in solution and can be introduced again into the cathode-compartment.

Example: The cathode-compartment of an electrolytic vat is charged with one thousand cubic centimeters of caustic-soda lye of three-per-cent. strength and one hundred grams of nitrobenzene, which are dissolved in three hundred grams of benzene, while the anode-compartment is charged with causticsoda lye of fiveer-cent. strength. The anodes and catho es will be of metal and preferably of iron or nickel. liquid is strongly agitated, and electric current to the extent of about one hundred and fifty ampere-hours at current density of two to four amperes per square 'decimeter of cathode-surface is passed, whereby about eighty to eighty five grams of nitrobenzene are thus converted into hydrazobenzene, while about 1520 grams only are reduced to worry benzene. Both reduction products dissolve in the benzene, and'when the reduction is completed they can be decanted easily from-the surface of the cathode liquid. By

adding the necessary quantity of hydrochloric acid to the solution in benzene the hydrazobenzene is converted into benzidine xhydrochlorid, which is readily soluble in water, while the azoxy benzene remains dissolved in the benzene, and therefore can easily be separated from the aqueous solution of benzidine hydrochlorid. The solution of azoxy benzene in benzene is then returned to the cathode-compartment, to-

ortion of-nitro benzene. Any other hydrazo derivative and the corresponding benzidine derivatives may be converted similarly into hydrazo benzene and benzidine in the above manner.

Instead of benzene other indifferent solvents, as toluene, xylene, ether, &c., may be employed, and instead of caustic soda the electrolyte may consist of caustic potash or of solutions of alkali saltsas, for instance, solution of common salt. Further, instead of dissolving the reduction products, as indicated in the example, in the nascent condition the indifferent solvent may be added during or Patented Oct. 16, 1906.

The cathode;

ICC

after. the electrolysis and the reduction p'r0d obtained by the electrolysis, thereby preucts extracted by nn'xin and stirring said venting the said roducts from depositing in solvent with the cathode liquid. a solid form and facilitating their removal What'I-;clai1nis from the cathode com artment.

'5 The herein-described manufacture of hy- In witness whereof have hereunto signed drazo derivatives by the electrolyticreduction my name, this 21st day of February, 1906,in of the corresponding nitro, azoxy and azo the presence of two subscribin witnesses. bodies suspended in an aqueous alkaline 'so- OTTO DIEFTENBACH. lution, which consists in addin a convenient Witnesses:

rq solvent-insoluble in water to the electrolyte, JEAN GRUND,

an order to dissolve the reduction products I CARL GRUND. 

